Android学习笔记 - 数据库篇 (SQLite)

1.SQLite介绍
 官方网站：http://www.sqlite.org/
 
2.SQLiteOpenHelper使用方法
 getReadableDatabase() //创建或打开一个只读的数据库
 getWriteableDatabase() //创建或打开一个可读写的数据库
 onCreate(SQLiteDatabase db) //创建数据库
 onOpen(SQLiteDatabase db) //打开数据库
 onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) //更新数据库
 close() //关闭数据库

 

3.在SQLOpenHelper的子类中，必须有该构造函数
 public DatabaseHelper(Context context, String name, CursorFactory factory, int version)

 

public class DatabaseHelper extends SQLiteOpenHelper {

    // 默认版本
    private static final int VERSION = 1;

    // 默认构造函数
    public DatabaseHelper(Context context, String name, CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    // 构造函数（用于创建数据库）
    public DatabaseHelper(Context context, String name) {
        this(context, name, null, VERSION);
    }

    // 构造函数（用于更新数据库）
    public DatabaseHelper(Context context, String name, int version) {
        this(context, name, null, version);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        System.out.println("onCreate is start...");
        db.execSQL("create table user( id int, name varchar(20) )");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        System.out.println("onUpgrade is start...");
    }
}

 

4.使用adb访问SQLite
 adb shell //进行linux命令行（调试环境）
 ls -l //相当于dir /w
 cd data //与cd相同
 sqlite3 dbname //进入SQL管理模式
 .schema //查看数据库中的表
 SQL语句 //可直接查询
 rm -r databases //循环删除目录

5.增、删、改、查

public class SQLiteActivity extends Activity {

    // 声明控件
    private Button btnCreate = null;
    private Button btnUpgrade = null;
    private Button btnInsert = null;
    private Button btnUpdate = null;
    private Button btnDelete = null;
    private Button btnSelect = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sqlite);

        // 寻找控件
        btnCreate = (Button) findViewById(R.id.btnCreateDb);
        btnUpgrade = (Button) findViewById(R.id.btnUpgradeDb);
        btnInsert = (Button) findViewById(R.id.btnInsertDb);
        btnUpdate = (Button) findViewById(R.id.btnUpdateDb);
        btnDelete = (Button) findViewById(R.id.btnDeleteDb);
        btnSelect = (Button) findViewById(R.id.btnSelectDb);

        // 创建数据库
        btnCreate.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                System.out.println("btnCreate on start...");
                DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
                helper.getReadableDatabase();
            }
        });

        // 更新数据库
        btnUpgrade.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                System.out.println("btnUpgrade on start...");
                DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb", 2);
                helper.getReadableDatabase();
            }
        });

        // 新增数据
        btnInsert.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                System.out.println("btnInsert on start...");
                DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
                SQLiteDatabase db = helper.getWritableDatabase();

                // 参数列表
                ContentValues params = new ContentValues();
                params.put("id", 1);
                params.put("name", "dier");

                // 表名、列名、参数列表
                db.insert("user", null, params);
            }
        });

        // 修改数据
        btnUpdate.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                System.out.println("btnUpdate on start...");
                DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
                SQLiteDatabase db = helper.getWritableDatabase();

                // 参数列表
                ContentValues params = new ContentValues();
                params.put("name", "stdier");

                // 表名、参数列表、WHERE子句、子句参数
                db.update("user", params, "id=?", new String[] { "1" });
            }
        });

        // 删除数据
        btnDelete.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                System.out.println("btnDelete on start...");
                DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
                SQLiteDatabase db = helper.getWritableDatabase();

                // 表名、列名、参数列表
                db.delete("user", "id=?", new String[] { "1" });
            }
        });

        // 修改数据
        btnSelect.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                System.out.println("btnSelect on start...");
                DatabaseHelper helper = new DatabaseHelper(SQLiteActivity.this, "studyDb");
                SQLiteDatabase db = helper.getWritableDatabase();

                //表名、查询字段、WHERE子句、子句参数、groupBy、having、orderBy
                Cursor cursor = db.query("user", new String[] { "id", "name" }, "id=?", new String[] { "1" }, null, null, null);
                while (cursor.moveToNext()) {
                    System.out.println("query name -> " + cursor.getString(cursor.getColumnIndex("name")));
                }
            }
        });
    }
}